JP3397375B2 - Pneumatic radial tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire having a belt reinforcing layer arranged radially outward of a belt layer.

[0002]

2. Description of the Related Art In recent years, high performance pneumatic radial tires with excellent high speed durability have been required due to higher performance of vehicles, maintenance of road networks, etc. One of the ways to satisfy this requirement is flatness. The so-called flat tires that have a smaller drive force and improved driving force are known.This type of flat pneumatic radial tire has a belt layer centrifugally outward in the tire radial direction when the tire rotates at high speed. At least one rubber-coated heat-shrinkable organic fiber cord, which is arranged substantially parallel to the tire circumferential direction over the entire width of the belt layer in the tire radial direction outside, in order to prevent the tire from protruding. Pneumatic radial tires with a layered belt reinforcement layer are known.

[0003]

The use of the heat-shrinkable organic fiber cord as the cord of the belt reinforcing layer is because the organic fiber cord shrinks during vulcanization and the reinforcing layer tightens the belt layer so that the belt layer is This is because it prevents centrifugal force from squeezing outward in the radial direction of the tire, but in conventional pneumatic radial tires where the flatness ratio is not so small, the heat-shrinkable organic fiber has a wide tire side part. The contraction force generated by the contraction of the cord is appropriately absorbed and relaxed, without causing deformation of the tire side parts, etc.
Although it is possible to prevent the belt layer from protruding outward in the radial direction of the tire, however, due to the further demand for a high-performance pneumatic radial tire, if the flatness ratio is made smaller, the shrinkage of the heat-shrinkable organic fiber cord is caused. Since the tire side part that absorbs and relaxes the shrinking force generated in the process becomes narrow, the shrinking force of the heat-shrinkable organic fiber cord causes the pneumatic radial tire to be excessively tightened, causing deformation of the tire side part. In addition, a phenomenon such as the bead portion rising from the rim will occur. As a result, the uniformity of the pneumatic radial tire is deteriorated and the high speed durability is deteriorated.

On the other hand, in the pneumatic radial tire of this type, the center portion of the drive wheel tends to start to wear mainly in the initial stage, and as a result, the mass of the center portion becomes small in the middle or end of wear. The amount of protrusion in the radial direction of the tire during traveling is reduced, and the protrusion of the shoulder portion having a relatively large mass is increased, and at the same time, the ground contact pressure to the shoulder portion is increased. As a result, the deformation of the side wall portion and the bead portion is increased, and as a result, a standing wave or the like is generated and high-speed durability is deteriorated.

An object of the present invention is to solve the problems of the pneumatic radial tire having a small flatness as described above and to provide a pneumatic radial tire having excellent high-speed durability.

[0006]

DISCLOSURE OF THE INVENTION As a result of various studies, the inventors of the present invention have found that at least two belt layers having cords intersecting each other and the belt layers radially outward of the belt layers and substantially the entire width of the belt layers. A pneumatic radial tire having a belt reinforcing layer covering the belt reinforcing layer, the belt reinforcing layer is divided into both side regions and a central region in the width direction, and the cord in the central region has a heat shrinkage rate and A pneumatic radial tire having a small modulus and cords in both regions extending in the tire circumferential direction while exhibiting at least substantially a corrugated shape at the time of application before vulcanization is configured.

The heat shrinkage ratio and modulus of the cord in the central region of the belt reinforcing layer are made smaller than those of the cords in both regions of the belt reinforcing layer, and this portion is deformed even during load rolling in the middle or end of wear of the tire. By making it easier, the external input applied to both sides of the belt reinforcement layer is reduced,
Belt end separation and bead failure can be reduced.

Further, as described above, the heat shrinkage rate in both regions of the belt reinforcing layer is increased and the modulus is increased. A cord with a large modulus cannot be vulcanized unless a prestretch amount can be secured from before vulcanization to during vulcanization, however, if the modulus is large enough to allow vulcanization, after vulcanization. Has a small heat shrinkage and can prevent deformation of tire side parts, etc., and also prevents the occurrence of standing waves and the like by preventing stretching due to centrifugal force during load rolling after vulcanization and belt end separation, The failure of the bead portion can be reduced and high-speed durability can be improved. Further, by arranging the cords on both sides of the belt reinforcing layer in a substantially sine curve, it is possible to absorb heat shrinkage.

[0009]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples without departing from the gist of the present invention. In FIG. 1, which is a schematic cross-sectional view of the pneumatic radial tire of the present invention, 1 is a carcass and may be one layer or plural layers, and 2 is a filler, and Shore A hardness is 75 ° (preferably in the range of 70 to 90 °). ) Used relatively hard. 3 is a bead, which is the same as the conventional one. Reference numeral 4 denotes a two-layer belt layer in which steel cords are arranged so as to intersect each other at 25 ° with respect to the tire circumferential direction, and the belt layer 1 covers substantially the entire width of the belt layer 1 outwardly in the tire radial direction. A belt reinforcement layer 5 of layers is arranged. The cord in the central area Wc of the belt reinforcing layer 5 is a nylon cord 1260d (denier) / 2, and the width is determined in consideration of the tire size and the like, but in the embodiment of the present invention, it is about 17% of the belt width. did.

Further, as a cord of both sides of the belt reinforcing layer, 100% modulus is at least 2000 kg / mm.
By using the organic fiber cord of ² , it is possible to realize the weight reduction of the tire without lowering the bending rigidity of the belt layer, and more effectively reduce the belt end separation, the failure of the bead part, etc. can do.

Further, the cords in the central region Wc may be parallel to the tire circumferential direction or may be biased, as shown in FIGS.
Further, the angle with respect to the tire circumferential direction can be appropriately set. The cords in the both side regions Ws of the belt reinforcing layer 5 show the arrangement state of the cords in the both side regions Ws as shown in FIG.
Aramid cord 1500d (denier) / 2 is arranged substantially in a sine curve or corrugation at the time of application before vulcanization, and prestretching is generally applied by 0.5 to 5% as shown in FIG. After vulcanization, as shown in FIG. 3B, the amplitude of the cord becomes small and the cycle becomes large. If desired, the cord can be extended in a substantially straight line.

Although FIG. 1 shows a structure in which one belt reinforcing layer 5 covering the entire width of the belt layer 1 is divided into a central region and both side regions, it covers the entire width of the belt layer 1. One belt reinforcing layer 5 is arranged, and further belt additional reinforcing layers are arranged on both sides of the belt reinforcing layer 5 outside the belt layer 4 in the tire radial direction. And the modulus of elasticity of the cords of the belt additional reinforcing layer arranged on both sides of the belt layer 4 to be smaller than the heat shrinkage ratio and the modulus of the cord and the cords of the belt additional reinforcing layer arranged on both sides of the belt layer 4 are attached before vulcanization. Can also be configured to at least substantially exhibit a sine curve or waveform.

The tire size of the examples and the comparative examples is 255 / 40ZR17, and the comparative example is the one in which the belt reinforcing layer in the central region of the embodiment of the present invention covers the entire width of the belt layer.

The uniformity shown in Table 1 was obtained under the measurement conditions based on the German standard (WDK) and was indexed with a comparative example being 100. The larger the index, the better. In addition, the high speed durability is that the pneumatic tire having a constant internal pressure is installed on the drum, and after applying a constant load, the tire speed is 10 km /
It is increased by increments of h and the speed until failure is measured, which is indexed with the comparative example being 100. The high speed durability at the end of wear was also tested in the same manner as the above high speed durability, and Comparative Example 1
It is indexed as 00. If the deformation is very large as seen in the comparative example, the uniformity measurement may not be possible in some cases.

[0015]

[Table 1]

As shown in Table 1, the examples of the present invention have improved uniformity and significantly improved high-speed durability at the end of wear as compared with the comparative examples.

[0017]

Since the present invention is constructed as described above, it has the following effects.

It is possible to prevent deformation of the tire side portion due to shrinkage of the heat-shrinkable cord of the belt reinforcing layer after vulcanization, and to reduce external input to the shoulder portion at the middle stage of wear or at the end stage of wear. The high-speed durability of the pneumatic radial tire can be improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is a plan view showing an arrangement state of cords in a central region of a belt reinforcing layer.

FIG. 3 is a plan view showing an arrangement state of cords in a side region of the belt reinforcing layer before and after vulcanization.

[Explanation of symbols]

1 ... Carcass 2 ・ ・ ・ ・ ・ ・ Filler 3 ... Bead part 4 ... Belt layer 5 ... Belt reinforcement layer

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Claims (4)

(57) [Claims] 1. A pneumatic radial tire having at least two belt layers having cords crossing each other, and a belt reinforcing layer which is radially outward of the belt layers and substantially covers the entire width of the belt layers. , The belt reinforcing layer is divided into both side areas and the central area in the width direction, the cord in the central area has a smaller heat shrinkage rate and modulus than the cords in both areas, and the cords in both areas are the same as before vulcanization. A pneumatic radial tire characterized in that it extends in the tire circumferential direction while exhibiting at least substantially a waveform when being attached. 2. The pneumatic radial tire according to claim 1, wherein the cords in the both side regions are organic fiber cords having a modulus of at least 2000 kg / mm ² . 3. The cord in the central region is a nylon cord,
The pneumatic radial tire according to claim 1 or 2, which is substantially parallel to the tire circumferential direction. 4. The pneumatic radial tire according to claim 1, wherein the cord in the central region is inclined in the tire circumferential direction.